Railway track circuit apparatus



' Feb. 16, 1943. A. E. DODD RAILWAY TRACK CIRCUIT APPARATUS Filed May31, 1941 3 3 i i m 9 56 11 $56 F :35 32.: F cr r; 1 W I j m Fig. 4.

A BY

lNV TOR 1 0044 HIS ATTORNEY Patented Feb. 16, 1943 BAIPWAY TRACK CIRCUITAPPARATUS Arthur E. Dodd, Edgewood, Pa., assignor to The Union Switch 8;Signal Company, Swissvale, Pa., a corporation of PennsylvaniaApplication May 31, 1941, Serial No. 395,925

7 Claims.

My invention relates to railway track circuit apparatus, and it hasparticular reference to the organization of apparatus into railway trackcircuits of the class wherein improved operating characteristics areobtained by varying the en- Railway track circuits are arranged in suchmanner that the track relay is controlled by an application of a shuntwhich decreases the energy available at the relay to hold it picked up.This factor of controlling a relay by the application of a shunt ratherthan by opening or interrupting the circuit, generally results inproviding the relay with characteristics that make it slow to releaseand quick to pick up, inasmuch as the pickup energy level of a relayordinarily is much higher than the drop-away level at which the relayreleases. In order, therefore, for a train shunt to be effective torelease the relay, the shunt must be sufficiently low in resistance toshunt away from the relay winding the increment of energy above thedrop-away energy level of the relay. This shunt, however, provides a lowresistance or short circuit path across the relay winding whichmaintains the flux in the relay for an appreciable interval of time, sothat a correspondingly long time interval is required for even a lowresistance train shunt to lower the energy level of the relay below itsdrop-away value. Hence, if the train shunt varies intermittently ineffectiveness, the release period of the relay might be materiallyincreased and after the relay releases due to a shunt, there is apossibility that these variations in shunt might cause the relay to bepicked up and released and thus follow the fluctuations in the appliedshunt. of ordinary relays to follow varying train shunts, and the slowreleasing characteristics possessed by such relays when shunted, areundesirable in track relays since such relays often are incorporatedinto signaling or control systems not only for controlling signalindications, but also, for establishing directional control inaccordance with the sequence in which the relays of two or moresuccessive sections are released. It is apparent, therefore, that if arelay is improperly picked up in response to a momentary loss of trainshunt, or if the relay of a section vacated by a, train picks up priorto the train causing the release of the relay of the section in advance,an improper directional set-up might be established as well as causingflashing signal indications,

etc. Furthermore, such relays are oftenemployed for electrically lockingsignals and ergization of the track relay after it has picked Thetendency switches against operation, and if a track relay isintermittently released and picked up due to a varying train shunt inits section, the effectiveness of such locking is materially decreased.

I am aware that schemes have been proposed heretofore to condition atrack relay to create its pick-up energy level when it is released, andto reduce the energy level in the relay after it has picked up, therebyobtaining a track circuit having high shunting characteristics. One ofthe most effective of such schemes is to employ a secondary relay, whichordinarily is slow to pick up, controlled by the track or primary relayand in turn controlling the release sensitivity of the track relay. Suchsystems commonly are termed primary-secondary track relay combinations,and although they materially improve the operation of track relays andtrack circuits, the use of two independent relays increases the initialand maintenance cost of such track circuit arrangement to a considerableextent.

In view of the foregoing and other important considerations, it is anobject of my invention to provide a track relay having means for c0ntrolling its own release sensitivity in such manner that the relay isconditioned to create its proper pick-up energy level when released, andwhen picked up the energy level in the relay is reduced to a value onlyslightly above that required to hold its armature in its attractedposition.

Another object of my invention is to provide a railway track circuitincorporating a track relay having means for incorporating into a singlerelay structure the functions of the two relays of a primary-secondaryrelay combination.

A further object of my invention is the provision of railway trackcircuit apparatus incorporating relays having means for delaying thepickup of the armatures of such relays.

An additional object of my invention is the provision of safe, reliable,and relatively inexpensive means for obtaining in a single relay thebenefits and advantages of a primary-secondary relay combination.

Another object of my invention is the provision of novel and improvedforms of electrical relays arranged to be slow to pick up and havingquick release characteristics when shunted.

The above-mentioned and other important objects and characteristicfeatures of my invention which will become readily apparent from thefollowing description, are attained in accordance with my invention byincorporating into a track relay a retaining winding coupled to a trackcircuit and arranged to oppose the attractive action of the operatingwinding of the relay on its armature, and by utilizing amake-before-break contact combination operated by such armature tocontrol the energy level created by the operating winding. The couplingof the retaining winding of the relay to the track circuit is effectedin accordance with my invention in such manner that the decay of fluxdue to current in the operating winding is not effected, but the growthof flux is prolonged to provide the relay with slow pick-upcharacteristics.

I shah describe four forms of apparatus embodying my invention, andshall then point out the novel features thereof in claims.

In the accompanying drawing, Fi 1 is 2. diagrammatic view showing apreferred form of apparatus embodying my invention. Figs. 2, 3 and 4 arediagrammatic views each illustrating a modified form of the apparatusshown in Fig. 1, and each also embodying my invention.

In each of the several views of the drawing, similar referencecharacters have been employed to designate corresponding parts.

Referring first to Fig. 1, the reference characters I and la designatethe track rails of a stretch of railway track divided by insulatedjoints 2 into an insulated section DE. Section DE is provided with atrack circuit comprising a suitable source of current, such as a batteryTB, connected in series with the usual current limiting resistor 3,across the rails I and la at one end D of the section, and at times onlya portion and at other times the entire operating winding of a relay TRconnected across the track rails at the other end E of the section.

Relay TR comprises a magnetizable core 5pmvided with an operatingwinding 8, another magnetizable core I provided with a retaining windingII, and armature means comprising two armatures I and 8 disposed inmagnetic relation to cores and II), respectively. and connected togetherby means of a rigid non-magnetic member 9. The armature means arebiased, as by gravity, into a released or back position wherein armature8 engages core III, and are operated to a front or picked-up position inresponse to the attractive action on armature I of the flux due tocurrent in winding 6. This operation of the armature means is at timesopposed by the attractive action on armature 8 of flux due to current inretaining winding II. Armature I is pivoted at 4 in the usual manner andhas associated therewith a plurality of contact members I2, I3 and I4which cooperate with the usual front and back contact points to formfront and back contacts according as armature I is in its picked-up orreleased position, respectively. One of the contact members I2 isbifurcated and functions as the common or bridging member of amake-before-break contact arrangement. When armature I is in itsattracted position, a portion only of winding 6 is connected across thetrack rails I and la at E over an obvious circuit including frontcontact I2-I5 and a resistor I1, and when armature I is released, theentire operating winding 6 is connected to the track rails over anobvious circuit including back contact I2I6.

The retaining winding II is coupled with the track circuit in suchmanner as to provide the relay with slow pick-up characteristics.Various means are provided to eifect this coupling. In Fig. 1, forexample, the retaining winding is coupled to the track circuit throughthe medium of a secondary winding I8 disposed on core 5 and connected toretaining winding l I through a back contact I3-I9 of armature I; inFig. 2 the coupling is effected through a condenser 20 (see Fig. 2)which may, for example, be of the electrolytic type, connected in serieswith retaining winding II across the track rails I and Ia in multiplewith winding 5 of relay TR; in Fig. 3 the coupling is effected throughthe medium of an auxiliary transformer 22 (see Fig. 3) having a primarywinding 23 interposed in series in the connection of winding Ii of relayTR to the track rails and having a secondary winding 24 connected overback contact I3I9 of armature I to retaining winding I I; and in Fig. 4the coupling is also effected by means of auxiliary transformer 22.

The operation of the apparatus illustrated in Fig. 1 is as follows: Whensection DE is unoccupied, armature I of relay TR is in its attracted orupper position as shown in the drawing, and in this position of armature1 front contact I2--I5 of relay TR is closed to complete the obviouscircuit path which connects resistor I! and a portion of coil 6 of relayTR across the rails I and la. The parts of relay TR preferably aredesigned and proportioned in such manner that with only a portion ofcoil 6 energized, an energy level only sufficiently above the releasevalue of the relay to assure reliable operation of such relay under thevarious ballast conditions, is created in the relay due to currentsupplied to the portion of coil 6 of the operating winding from therails I and 1a.

When a train enters section D--E, the current supplied from the battery'I'B to the rails I and I a. is shunted away from the operating winding6 of relay TR. Since the relay armature is held attracted by an energylevel only slightly in excess of its release value, the shunt applied tothe relay causes the energy level in the relay to decrease and as aresult armature I quickly drops to its released position, whereincontact members I2, I3 and I4 engage their respective back contactpoints. During the travel of armature I from its attracted to itsreleased position, contact member I2 makes engagement with back contactpoint I6 prior to breaking engagement with front contact point I5,thereby avoiding opening of the relay circuits.

In the released position of armature I of relay TR, back contact I3--I9is closed to connect; retaining winding II to secondary windingMidisposed on core 5. Also, resistor I is placed on open circuit and theentire operating winding ii of relay TR is connected across the trackrails I and la over back contact I2-IB, thereby conditioning the relayto create its pick-up energy level. When the train shunt is removed fromrelay TR, as for example, when the train vacates section DE or when theshunt is momentarily lost due to rail film conditions or other poorshunting conditions, current from battery TB is supplied through rails Iand la to the entire operating winding 6 of relay TR. During thebuilding up of flux in core 5 dueto such current, an electromotive forceis induced in the secondary winding I8 disposed on core 5 and is appliedthrough back contact I3-I9 to retaining winding II. The flux set up dueto current in winding Ii threads armature 8 to hold that armature downand thus opposes the action on armature 1 of the flux due to current inwinding 6. If the energization of the relay operating winding is causedb'y'the train vacating the section, the action of winding II in opposingthe pick-up eifect of the flux due to current in winding 6 i lnotions tomaintain armature 1 released until the flux condition in core reachessubstantially a constant state condition so that no electromotive forcesare induced in secondary winding I8. This steady state flux condition incore 5 substantially corresponds to the pick-up energy level of therelay, and since under the condition of flux equilibrium in core 5 nocurrent is induced in winding I8, the attractive effect of the flux dueto current in winding 6 on armature I is no longer opposed by theattractive effect on armature 8 of flux due to current in winding II,with the result that armature I is operated to its picked-up positionwherein back contact I3--I9 is opened to disconnect retainingwinding I Ifrom secondary winding I8, and contact member I2 is operated from itsreleased to its attracted position to form front contact I2--I5 prior tbreaking engagement with back contact point IS. The closing of frontcontact I2--I5 connects resistor I! in circuit with a portion ofoperating winding 5 of relay TR across the track rails I and Ia, hencearmature I of relay TR is held in its attracted position by virtue ofthe energization of only a portion of the operating winding 8 of relayTR and the energy level of the relay accordingly is reduced to a valueonly slightly greater than the release value of the relay, as waspointed out heretofore. Resistor I1 is selected to have a resistancesubstantially equal to the resistance of the portion of winding 6 thatis cut out when the relay is picked up, hence the resistance of therelay is substantially the same in both its released and picked-uppositions, and the percentage reduction of flux, effected when the relayis picked up, iscaused to be independent of the track circuit length andadjustment. Relay TR accordingly is caused to be slow to pick up, andwhen the train vacates its associated section, the pickup of theassociate. relay is delayed for an interval suflicient to enable thetrain to shunt the relay of the section in advance and cause suchadvance track relay to be released to establish the proper directionalset-up, signal control, locking, or other function wherein it isrequired for proper operation that the advance relay be released priorto the rear relay picking up.

In the event that armature I of relay TB. is released so that its entireoperating winding 8 is connected in circuit with the track rails, and

current is supplied from the rails to such winding due to a loss ofshunt in section D-E, then retaining winding II is energized by currentsupplied from secondary winding I8 during the building up of flux incore 5 and armature I is held down due to the attractive effect onarmature 8 of flux due to current in retaining winding I I. Thishold-down effect of winding I I prevents armature I of relay TR frompicking up immediately on a loss of shunt, and provides a delayedpick-up period for relay TR sufiicient under normal conditions to enablethe train shunt to be restored and the winding 6 again to be shuntedprior to armature 'I being attracted from its released to its picked-upposition. It can be-seen, therefore, that the delayed responsecharacteristics of a relay of the class illustrated in Fig. l preventsimproper operation of the relay due to a momentary loss of train shuntin its associated section.

It should be noted that the contacts operated I2 of relay TR function ascontacts during the travel of from its released to its by contact membermake-before-break the relay armature picked-up position, that is, frontcontact I2--I5 is closed prior to back contact I2--I6 being opened. Inaddition, the operation of these contacts is effected by the travel ofarmature I from its released to its picked-up position only after thepick-up energy level is created in the relay, hence armature I isattracted in response to a relatively high energy level available in therelay and moves rapidly due to the magnetic force present in the relay.The momentum developed due to the rapid movement of armature I is,therefore, sufficient to carry the armature to its fully attractedposition even though the energy level in the relay is reduced when backcontact I2-I6 opens. With armature I in its fully attracted position,the reduced energy level available in the relay after front contactI2-I5 closes is effective to maintain the armature in its,

picked-up position.

In addition, it should be noted that secondary winding I8 disposed onrelay core 5 is open circuited at all timesexcept when back contact I3l9of the relay is closed and it follows that when armature I is picked up,winding I8 cannot operate to delay the decay of relay flux such as mighthappen if winding I8 were connected at all times in circuit withretaining winding Ii.

I have represented in Fig. 2 a modified arrangement of the relay shownin Fig. 1, wherein retaining winding II is coupled to the track circuitthrough a condenser 20 which is charged when the section becomesunoccupied, and which discharges through retaining winding I I and thetrain shunt when the section becomes occupied. During the interval thatcondenser 20 becomes charged, winding II is energized and functions tohold down armature 8 and thus oppose operation of armature I. Forexample, when relay TR is shunted, armatures 1 and 8 are released andcondenser 20 is discharged. When the shunt is removed, the chargingcurrent of the condenser flows through retaining winding II and ofcourse is effective to energize winding II to create flux which tends tohold armature B in its released position against the attractive effecton armature I of flux due to current in winding 6, thereby rendering therelay slow to pick up. When the section becomes occupied, the condenserdischarges through winding II and the low resistance train shunt, butthis action has little or no effect upon operation of the relay at thistime other than to condition the condenser to become charged again whenthe section becomes vacated. It is, of course, readily apparent that byproperly proportioning condenser 20, the relay shown in Fig. 2 may beprovided with slow pick-up characteristics substantially similar tothose pointed out in connection with relay TR of Fig. 1. It is furtherapparent that the relay shown in Fig. 2 functions to vary the energylevel in the relay after it picks up in substantially the same mannerthat such energy level is varied by the apparatus represented in Fig. 1.

The apparatus represented in Fig. 3 illustrates a further modificationof the apparatus of Fig. 1

wherein retaining winding II is coupled to the track circuit by means ofa transformer 22 having its primary winding 23 interposed in theconnection of winding 8 to the track rails. Secondary winding 24 oftransformer 22 is connected to retaining winding II when back contactI3-I9 is closed, and it is readily apparent that the apparatus shown inFig. 3 will operate in substantially the same manner as that illustratedin Fig. 1 to provide slow pick-up characteristics and vary the energylevel of the relay after it picks up.

A still further modification of the apparatus illustrated in Fig. 1 isrepresented in Fig. 4, wherein a polarized relay TRI is interposed in apolarized track circuit supplied with unidi-' rectional current of onerelative polarity or another from battery TB according as pole changingcontacts 26 and 21 are in their picked-up or released positions,respectively. Relay TRI is ance with the polarity of current energizingopcrating winding 8 of th relay.

Relay 'I'Rl, as shown, is provided with an auxiliary magnetic structure30 carrying retaining winding II and provided with a core extension I 0arranged to hold down armature 8 when winding H is energized. Coreextension I0 of relay 'IRI therefore corresponds to auxiliary cores l0shown in Figs. 1, 2 and 3. When armature I of relay TRI is in its upperattracted position, armature .8 is operated into magnetic relation tocore 30 so that when winding H is energized, armature 8 is attracted tocore 30 and functions to hold armature 'l in its upper position. WindingII is connected to secondary winding 24 of transformer 22 which has itsprimary winding 23 interposed in the connection of operating winding 6of relay 'I'Rl to the track rails. Relay 'I'RI also incorporates themake-betore-break contact arrangement hereinbei'ore described and bymeans of which the energy level in the relay is varied according as therelay is released and picked up.

When section DE is unoccupied and pole changing contacts 28 and 21 arein their upper positions as shown in the drawing, current of onerelative polarity which I shall term positive polarity is suppliedthrough the track rails l and la to a portion of operating winding 6 ofrelay TRI. The parts of relay TRI are so proportioned that with only aportion of winding 8 energized, the energy level created in the relay issufiicient to hold neutral armature l in its upper attracted position,and with relay 'I'Rl energized with current of normal polarity, polarcontact member 28 is operated to its normal oi. left-hand position, asviewed in the drawing.

If, now, pole changing contacts 26 and 21 operate to their releasedpositions, current of the opposite or reverse polarity is appliedthrough transformer 22 to operating winding 8 of relay TRI. During theinterval of flux reversal in transformer 22, an electromotive force isinduced in secondary winding 24 of the transformer and is applied toretaining winding II to energize that winding and attract auxiliaryarmature 8. The parts of relay 'IRl are so proportioned that theenergization of retaining winding ll efiected due to a reversal ofcurrent in winding 23 ottransformer 22 is effective to hold armature 8in its upper position until the flux in core 5 builds up to its valuesufllcient to hold armature I in its attracted position. It follows,therefore, that neutral armature 1 of relay TB! is held in its upperattracted position during the intervals of current reversals in thetrack circuit. Under the assumed conditions, polar contact member 29will of course be caused to operate to its reverse or right-handposition, as viewed in Fig. 1.

When section D-E becomes occupied by a train, the current supplied frombattery TB is shunted away from operating winding 5 of relay TRI andneutral armature l releases to open front contact I2l5 and close backcontact lZ-lB, the closing of this latter contact conmeeting the entireoperating winding 6 of relay 'IRI in circuit with the track rails. Whenthe section becomes vacated, therefore, the entire operating winding ofrelay TRI is available to create flux and pick up neutral armature 1.However, the energizatlon of operating winding -6 of relay TR! causesthe induction in secondary winding 24 or transformer 22 of anelectromotive force which energizes winding H and causes flux to threadcore extension l0 and armature 8 to hold armature 7 down against theattractive effect of flux due to current in winding 5. After the currentin winding 6 attains substantially a constant state condition, windingIt becomes deenergized and no longer opposes the attractive effect offlux due to current in winding 6 on armature 1, so that the armaturemoves rapidly from its released to its attracted position, therebyopening back contact l2-l6 and closing front contact i2l5. The closingof front contact l2-l5 of course results in the energization of only aportion of operating winding 6 of relay TRI, and the energy levelcreated in the relay is therefore reduced to a value only slightlygreater than the releasevalue or the relay. It follows, therefore, thatrelay ml is made slow to pick up, is held in its attracted positionduring inter vals of reversals of current polarity in the oper atingwinding of the relay, and the energy level in the relay is variedaccording as the relay is released or picked up in order to attain moresatisfactory shunting characteristics for the relay.

Although I have herein shown and described only four forms 01' trackcircuit apparatus embodying my invention, it is understood that variouschanges and modifications may be made therein within the scope of theappended claims without departing from the spirit and scope of myinvention.

Having thus described my invention, what I claim is:

1. In combination, a magnetizable core, armature means disposed inmagnetic relation to said core and provided with contacts including amake-before-break contact combination comprising a front contact and aback contact with a bridging member which causes both said contacts tobecome closed momentarily during the movement of said armature meansfrom its released to its attracted position, an operating windingdisposed on said core and effective when energized to actuate saidarmature means from its released to its picked-up position, a controlcircuit connected to a portion only of said operating winding over saidfront contact and to the entire operating winding over said backcontact, a retainingwinding disposed to be efiective when energized tooppose the attractive action of said operating winding on said armaturemeans, and a condenser connected in series with said retaining windingacross said control circuit in multiple with said operating winding.

2. In combination, a magnetizable core, armature means disposed inmagnetic relation to said core and provided with contacts including amake-before-break contact combination comprising a front contact and aback contact with a bridging member which causes both said contactsdisposed on said core and efiective when energized to actuate saidarmature means from its released to its picked-up position, a controlcircuit connected to a portion only of said operating winding over saidfront contact and to the entire operating winding over said backcontact, a retaining winding disposed to be effective when energized tooppose the attractive action of said operating winding on said armaturemeans, and a transformer having a primary winding interposed in theconnection of said operating winding to said control circuit and havinga secondary winding connected to said retaining winding over a backcontact operated by said armature means.

3. In combination, a magnetizable core, an armature disposed in magneticrelation to said core, an operating winding on said core for actuatingsaid armature, contacts operatively connected to said armature andoperated from one position to another in response to energization ofsaid operating winding, 3. control circuit connected to a portion onlyof said operating winding over a contact of said armature closed in itssaid other position and connected to the entire operating winding over acontact of said armature closed in its said one position; and aretaining winding supplied with current during a growth of flux in saidcore due to current in said entire operating winding, said retainingwinding being disposed so as to be effective when energized to retainsaid armature in its said one position in opposition to the attractiveaction of said operating winding on said armature.

4. In combination with a control circuit, a niagnetizable core, anarmature disposed in magnetic relation to said core, an operatingwinding connected to said control circuit and disposed on said core foractuating said armature, contacts operatively connected to said armatureand including a front contact operated from an open to a closedcondition in response to operation of said armature from its released toits attracted position caused by energization of said operating winding,a retaining winding inductively coupled to said control circuit whensaid armature is released and disposed to oppose the attractive action01' said operating winding on said armature, and means controlled bysaid front contact for decreasing the energization of said operatingwinding by said control circuit, whereby said op-- erating winding isconditioned to create a high or a low energy level in the core accordingas said armature is released or is picked up.

5. In combination, a magnetizablc core, an op crating winding disposedon said core, an arma ture disposed in magnetic relation to said coreand provided with contacts including a makebefore-break contactcombination comprising a front contact and a back contact with a,bridging member which causes both said contacts to become closedmomentarily during the movement of said armature from its released toits attracted position, a control circuit connected over said frontcontact to a portion only or said operating winding and connected oversaid back contact to the entire operating winding, 2. retaining windingdisposed to oppose the attractive action of said operating winding onsaid armature, and a secondary winding disposed on said core andconnected to said retaining winding over a back contact operated by saidarmature.

6. In a relay, in combination, two magnetizable cores, an armaturebiased away from one toward the other 01' said cores, an operatingwinding on said onecore for actuating said armature to said one core,contact members controlled by said armature from one position to anotherin response to the energization of said operating winding, a retainingwinding disposed on said other core and eil'ective when energized todelay the response 0! said armature to energize.- tion of said operatingwinding, and means including a secondary winding disposed on said onecore and a contact closed in said one position of said contact membersfor energizing said retaining winding.

7. In combination, two magnetizable cores, an armature biased away fromone toward the other of said cores, an operating winding on said onecore for actuating said armature against its bias to said one core,contacts operatively connected with said armature and operated from oneposition to another when said armature is actuated to said one core, acontrol circuit, means controlled by contacts of said armature forconnecting only a portion of said operating winding with said controlcircuit when said other position and for connecting the entire operatingwinding with said control circuit when said contacts occupy their saidone posi tion, a retaining winding disposed on said other core, andmeans for supplying energy to said re taining winding during the growthof flux in said one core due to cm nt in said entire operating winding,whereby energy in said retaining wind ing creates firm actin on saidarmature in opposition to the flux created by energy in said entireoperating winding for delaying actuation of said armature from saidother core to said one core.

ARTHUR E. DODD.

said contacts are in

